Battery pack and thermal runaway monitoring method therefor, and vehicle

Abstract

A battery pack (100) and a thermal runaway monitoring method therefor, and a vehicle. The battery pack (100) comprises: a battery module (10), comprising multiple successively stacked battery cells (11); end plates (20), arranged at the ends of the battery module (10) along the stacking direction of the battery cells (11); a monitoring structure (30), arranged on the side surface of at least one battery cell (11) parallel to the end plate (20), and configured to monitor a swelling deformation value of the battery cell (11); and a BMS (40), electrically connected to the monitoring structure (30), and configured to calculate the degree of deformation and a deformation rate within a preset time on the basis of the swelling deformation value, so as to determine whether the battery pack (100) is in a thermal runaway state on the basis of the degree of deformation and the deformation rate.

Description

Battery pack, vehicle and thermal runaway monitoring method thereof

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on November 27, 2023, with application number 2023116027056. The entire contents of the above application are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of battery technology, and in particular to a battery pack, a vehicle, and a method for monitoring thermal runaway thereof. Background Art

[0003] The battery pack is a core component of new energy vehicles, providing the energy they need to operate. During use, the battery pack may experience thermal runaway due to manufacturing defects or extreme conditions such as strong impact, causing the cells within the battery pack to swell and deform.

[0004] When a battery pack experiences thermal runaway, a warning signal must be issued five minutes before the thermal runaway reaches the passenger compartment, allowing passengers sufficient time to escape and ensuring their safety. Thermal runaway monitoring for battery packs typically involves monitoring temperature or voltage signals. Technical issues

[0005] When collecting temperature signals in related technologies, the NTC that collects temperature is easily affected by the environment; or when a vehicle travels from a low-altitude area to a high-altitude area, the pressure signal will also change significantly, resulting in false alarms. Technical Solutions

[0006] In a first aspect, the present application provides a battery pack, comprising: a battery pack, comprising a plurality of single cells stacked in sequence; an end plate, arranged at the end of the battery pack along the stacking direction of the single cells; a monitoring structure, arranged on at least one side parallel to the single cell and the end plate, configured to monitor the expansion deformation value of the single cell; a BMS, electrically connected to the monitoring structure, configured to calculate the deformation rate and the deformation rate within a preset time based on the expansion deformation value, so as to determine whether the battery pack is in a thermal runaway state based on the deformation rate and the deformation rate.

[0007] In a second aspect, the present application provides a vehicle comprising a main body and the above-mentioned battery pack, wherein the battery pack is installed on the main body.

[0008] In a third aspect, the present application provides a method for monitoring thermal runaway of a battery pack, comprising: obtaining the expansion deformation value ΔL of a single battery in the battery pack through a monitoring structure, and calculating the deformation rate of the single battery according to the expansion deformation value ΔL and the deformation rate F(t) within the preset time t; determining the deformation rate Whether it is within a first preset range, and whether the deformation rate F(t) is within a second preset range; if so, it indicates that the battery pack is in a thermal runaway state. Beneficial effects

[0009] Since the single battery expands in the direction of the large surface when thermal runaway occurs, a monitoring structure is set on the side parallel to the single battery and the end plate. When thermal runaway occurs, the expansion deformation value of the single battery after expansion is monitored by the monitoring structure. The expansion deformation value is transmitted to the BMS. The BMS obtains the deformation rate and the deformation rate within the preset time through the expansion deformation value. The BMS responds to the deformation rate according to the deformation rate. And the deformation rate determines whether the battery pack is in a state of thermal runaway. If so, the BMS can take the next alarm action. In this way, by monitoring the expansion deformation value of the single battery in the battery pack after expansion when thermal runaway occurs, the basis for judging whether the battery pack is in a state of thermal runaway can be obtained. Compared with the method of monitoring the temperature change or pressure change of the battery pack, it is less affected by the surrounding environment and has higher accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG1 is a schematic structural diagram of a battery pack according to an embodiment of the present application;

[0011] FIG2 is a schematic structural diagram of the battery pack in FIG1 under normal use;

[0012] FIG3 is a schematic structural diagram of the battery pack in FIG1 in a thermal runaway state;

[0013] FIG4 is a schematic structural diagram of the single battery in FIG1 in a thermal runaway state;

[0014] FIG5 is a schematic structural diagram of the monitoring structure in FIG2 ;

[0015] FIG6 is a flow chart of a method for monitoring thermal runaway of a battery pack according to another embodiment of the present application.

[0016] The meanings of the reference numerals are as follows:

[0017] 100-battery pack, 10-battery group, 11-single battery, 20-end plate, 30-monitoring structure, 31-strain gauge, 32-insulating protective part, 40-BMS, 50-insulating sheet. Modes for Carrying Out the Invention

[0018] Please refer to Figures 1 to 5, which show a battery pack 100 provided in an embodiment of the present application, including a battery group 10, an end plate 20, a monitoring structure 30 and a BMS 40.

[0019] 1 to 3 , a battery pack 10 includes a plurality of sequentially stacked single cells 11; an end plate 20 is disposed at an end of the battery pack 10 along the stacking direction of the single cells 11; a monitoring structure 30 is disposed on a side parallel to at least one of the single cells 11 and the end plate 20 and is configured to monitor the expansion deformation value ΔL of the single cell 11; a BMS 40 is electrically connected to the monitoring structure 30 and is configured to calculate a deformation rate based on the expansion deformation value ΔL. And the deformation rate F(t) within the preset time t, according to the deformation rate and the deformation rate F(t) to determine whether the battery pack 100 is in a thermal runaway state.

[0020] In the battery pack 100, since the single cell 11 expands in the direction of the larger surface when thermal runaway occurs, a monitoring structure 30 is provided on the side parallel to the single cell 11 and the end plate 20. When thermal runaway occurs, the monitoring structure 30 monitors the expansion deformation value ΔL of the single cell 11 after expansion. The expansion deformation value ΔL is transmitted to the BMS 40, and the BMS 40 obtains the deformation rate according to the expansion deformation value ΔL. And the deformation rate F(t) within the preset time, BMS40 calculates the deformation rate according to the deformation rate and deformation rate F(t) to determine whether the battery pack 10 is in a thermal runaway state. If so, the BMS 40 can perform the next alarm action. In this way, by monitoring the expansion deformation value △L of the single battery 11 in the battery pack 10 after expansion when thermal runaway occurs, the basis for judging whether the battery pack 100 is in a thermal runaway state can be obtained. Compared with the method of monitoring the temperature change or pressure change of the battery pack 100, it is less affected by the surrounding environment and has higher accuracy.

[0021] In some embodiments, the single cells 11 are prismatic cells. When forming the battery pack 100, the prismatic cells have side surfaces parallel to the end plates 20. These side surfaces are the larger surfaces of the prismatic cells. When thermal runaway occurs, the prismatic cells expand and deform toward the larger surfaces, and this expansion and deformation occurs very quickly. Therefore, the expansion and deformation of the single cells 11 during thermal runaway can be monitored by the monitoring structure 30. The BMS (battery management system) is configured to monitor the battery status, prevent overcharging and overdischarging, and extend the battery life. It is also configured to detect thermal runaway conditions to ensure battery safety during use.

[0022] Specifically, in some embodiments, the monitoring structure 30 includes a strain gauge 31, which is a device for measuring the strain of an object and includes an insulating substrate and a metal sensitive grid. During measurement, the strain gauge 31 is attached to the surface of the object, for example, by gluing it to the large surface of the single cell 11. When the single cell 11 expands and deforms due to thermal runaway, the sensitive grid also deforms, causing a corresponding change in the resistance of the sensitive grid. By receiving the tiny change in the resistance of the sensitive grid, it can be converted into the actual strain value of the single cell 11, thereby obtaining the expansion deformation value ΔL of the single cell 11.

[0023] Please refer to Figure 5. When the strain gauge 31 is adhered to the large surface of the single cell 11, due to the arrangement of the wiring harness on the strain gauge 31, such as the position of the welding foot, there will be a bulge on a part of the strain gauge 31. In order to prevent the bulge from damaging the surface of the single cell 11, in some embodiments, the battery pack 100 also includes an insulating protective member 32, and the insulating protective member 32 is covered on the outside of the monitoring structure 30. In this way, by arranging the insulating protective member 32 outside the strain gauge 31, the insulating protective member 32 can wrap the bulge, thereby avoiding the risk of the bulge directly contacting the surface of the single cell 11 when the strain gauge 31 is adhered to the surface of the single cell 11, which may cause the protective film of the single cell 11 to be scratched.

[0024] Specifically, in some embodiments, the insulating protective member 32 is a mica roll, which is an insulating material formed by using mica paper as a base material, glass fiber or ceramic fiber as a reinforcing material, resin bonding, and drying. At the same time, a backing adhesive can be provided on the surface of the mica roll, which can directly drive the strain gauge 31 to be adhered to the surface of the single cell 11, thereby facilitating the installation of the strain gauge 31.

[0025] Specifically, in some embodiments, the thickness of the strain gauge 31, including the mica paper covering the strain gauge 31, ranges from 0.2 mm to 0.3 mm. This smaller thickness can avoid affecting the installation of the entire battery pack 100 and increasing the length of the battery pack 100 along the stacking direction of the battery cells 11, thereby controlling the length of the battery pack 100 within a reasonable range. For example, the thickness of the strain gauge 31, including the mica paper, can be set to 0.2 mm, 0.22 mm, 0.24 mm, 0.26 mm, 0.28 mm, or 0.3 mm, corresponding to the thickness of different battery cells 11, but this is not a limitation.

[0026] Referring to Figures 2 and 3 , in some embodiments, when a monitoring structure 30 is disposed within a battery pack 10, to ensure the safety and service life of the battery pack 10, the monitoring structure 30 is disposed on the individual cells 11 at the ends of the battery pack 10 along the stacking direction of the individual cells 11, and is disposed on the side of the individual cells 11 facing the end plate 20. Figure 2 is a schematic diagram of the battery pack 10 in normal use, and Figure 3 is a schematic diagram of the battery pack 10 in use after expansion due to thermal runaway.

[0027] Specifically, please refer to Figure 1. Since there is an insulating sheet 50 between the end plate 20 and the battery pack 10, the monitoring structure 30 is arranged between the insulating sheet 50 and the battery pack 10, so that the monitoring structure 30 is arranged at the end of the battery pack 10 to avoid affecting the normal expansion of the entire battery pack 10 during use, thereby ensuring the service life of the battery pack 10 and also ensuring the safety of the battery pack 10 during use; at the same time, since the monitoring needs to be electrically connected to the BMS40, the monitoring structure 30 is arranged at the end of the battery pack 10. This can reduce the installation cost of the monitoring structure 30 and facilitate the electrical connection with the BMS40 after the wiring harness is wound.

[0028] Thus, through the installation of the above-mentioned monitoring structure 30, when a single cell 11 in the battery pack 10 expands due to thermal runaway, for example, when a single cell 11 located in the center area expands, the large surface of the single cell 11 expands and deforms, and is transmitted to the single cell 11 at the end in turn, so that the expansion deformation value △L of the single cell 11 can be monitored by the monitoring structure 30 located at the end.

[0029] In some embodiments, to more accurately monitor thermal runaway conditions of the battery pack 10 during use, monitoring structures 30 are provided on the individual cells 11 at both ends of the battery pack 10. This allows for more accurate monitoring of the expansion of the individual cells 11 throughout the battery pack 10, enabling more precise control instructions to be issued by the BMS 40. In some embodiments, while ensuring normal expansion of the individual cells 11 and reducing the installation cost of the monitoring structures 30, a monitoring structure 30 may be installed at every 1 / 3, 1 / 4, or 1 / 5 of the stacked cells 11. This allows for more accurate monitoring of the deformation of the individual cells 11 after expansion, while also appropriately reducing the installation cost of the monitoring structures 30.

[0030] The single cell 11 is in a normal use state as shown in FIG1 , and the state after the single cell 11 expands due to thermal runaway is shown by the dotted lines in FIG3 and FIG4 .

[0031] Among them, according to the expansion deformation value △L, the deformation rate is obtained When determining whether the battery pack 10 has thermal runaway using the deformation rate F(t), for example, referring to FIG4 , the original thickness L1 of the single battery 11 is 25 mm. Within a preset time t, for example, at t=3 s, the single battery 11 undergoes thermal expansion, and the thickness increases from L1=25 mm to L2=30 mm. For example, the dotted lines in FIG3 and FIG4 indicate the state of thermal expansion. At this time, the expansion deformation value of the single battery 11 is △L=5 mm, and the deformation rate F(t) is ΔL=5 mm. =(L2- L1) / L1=2%, deformation rate If the deformation rate value of 2% and / or the deformation rate value of 0.67% are both within the preset range of thermal runaway, it means that thermal runaway has occurred in the single battery 11.

[0032] Specifically, in some embodiments, the deformation rate of the single battery 11 when thermal runaway occurs is set to and the deformation rate F(t) are in the following ranges:

[0033] 2%< <8%; and / or 0.4% / s<F(t)<2% / s.

[0034] If the BMS 40 calculates the deformation rate according to the expansion deformation value ΔL of the single battery 11 monitored by the monitoring structure 30 If the temperature and / or deformation rate F(t) meet the above range, it means that the battery pack 100 is in a thermal runaway state, and the BMS 40 needs to take the next alarm action.

[0035] The battery pack 100 is provided with a monitoring structure 30 in the battery pack 10 to monitor the expansion deformation value ΔL of the single battery 11 through the monitoring structure 30. The expansion deformation value ΔL is transmitted to the BMS 40, and the BMS 40 calculates the deformation rate. and deformation rate F(t), if the deformation rate If the deformation rate F(t) and the deformation rate F(t) both meet the set range when the single battery 11 is in thermal runaway, it means that the single battery 11 has experienced thermal runaway, and the BMS 40 can issue a warning signal to ensure that the occupants can evacuate safely.

[0036] Please refer to FIG6 , which shows a method 200 for monitoring thermal runaway of the battery pack 100 according to a second embodiment of the present application, including the following steps:

[0037] Step S21: Obtain the expansion deformation value ΔL of the single battery 11 in the battery pack 100 through the monitoring structure 30, and calculate the deformation rate of the single battery 11 according to the expansion deformation value ΔL. And the deformation rate F(t) within the preset time t, where the initial thickness of the single battery is L1, the thickness after expansion during thermal runaway is L2, the expansion deformation value △L= L2- L1, and the deformation rate of the single battery 11 = (L2- L1) / L1*100%, deformation rate .

[0038] Prior to this step, a monitoring structure 30 and a battery pack 100 are provided. The battery pack 100 includes a single cell 11 and an end plate 20 provided at the end in the stacking direction of the single cell 11, and the end plate 20 is provided parallel to the large surface of the single cell 11. The single cell 11 can be a square battery, which can be an aluminum shell battery or a secondary battery such as a blade battery. When a single cell 11 or multiple single cells 11 in the battery pack 10 undergo thermal expansion, the expansion will occur toward the large surface of the single cell 11, and the single cells 11 will be transmitted to each other, causing the surrounding single cells 11 to expand. In this way, the monitoring structure 30 located at the end can monitor the thermal runaway state of the battery pack 10.

[0039] In some embodiments, the monitoring structure 30 includes a strain gauge 31 and an insulating protective member 32 covering the strain gauge 31. When a cell 11 expands and deforms during thermal runaway, the resistance of the strain gauge 31 changes accordingly. The resulting resistance change can be converted into an actual strain value, thereby obtaining the expansion deformation value ΔL of the cell 11. Furthermore, by covering the strain gauge 31 with the insulating protective member 32, the strain gauge 31 may have protrusions due to the wiring harness configuration, such as the location of the weld legs. To prevent these protrusions from damaging the surface of the cell 11, in some embodiments, the battery pack 100 further includes an insulating protective member 32 covering the monitoring structure 30. This prevents the strain gauge 31 from adhering to the surface of the cell 11, where the protrusions directly contact the surface of the cell 11 and risk scratching the protective film of the cell 11.

[0040] Specifically, in some embodiments, the insulating protective member 32 is mica paper, and the mica paper is provided with adhesive backing, so that the entire monitoring structure 30 can be conveniently and directly adhered to the surface of the battery.

[0041] In some embodiments, before measurement, the monitoring structure 30 is mounted on a side of at least one of the battery cells 11 and the end plate 20 that is parallel to each other.

[0042] Among them, when the monitoring structure 30 is set in the battery pack 10, in order to ensure the safety of use and the service life of the battery pack 10, the monitoring structure 30 is set on the single cell 11 at the end of the battery pack 10 along the stacking direction of the single cell 11, and is set on the side of the single cell 11 facing the end plate 20. In order to more accurately monitor the thermal runaway of the battery pack 10 during use, in some embodiments, the single cells 11 at both ends of the battery pack 10 are provided with a monitoring structure 30. In this way, the expansion of the single cells 11 in the entire battery pack 10 can be more accurately monitored, so that control instructions can be issued more accurately through the BMS40. In some embodiments, while ensuring that the single battery 11 can expand normally and at the same time reducing the installation cost of the monitoring structure 30, a monitoring structure 30 can be installed at every 1 / 3 position, or a monitoring structure 30 can be installed at every 1 / 4 position, or a monitoring structure 30 can be installed at every 1 / 5 position along the stacking direction of the single battery 11. In this way, the deformation of the single battery 11 after expansion can be accurately monitored, and the installation cost of the monitoring structure 30 can also be appropriately reduced.

[0043] After the battery pack 100 is installed, the expansion deformation value ΔL of the single battery 11 is obtained by the monitoring structure 30 in this step, and the deformation rate can be obtained by ΔL. And the deformation rate F(t) within the preset time t is used for the next step of judgment.

[0044] The expansion deformation value ΔL in this step refers to the actual expansion deformation of the single battery 11 after expansion that can be monitored by the monitoring structure 30 when the single battery 11 expands. For example, the original thickness L1 of the single battery 11 is 25mm. Within a preset time period, for example, at the preset time t=3s, the thickness of the single battery 11 increases from 25mm to L2=30mm. At this time, the expansion deformation value of the single battery 11 is ΔL=5mm, and the deformation rate is =(L2- L1) / L1=2%, deformation rate When the original thickness L1 of the single battery 11 is 25 mm, within the preset time t, for example, at t=4s, the thickness of the single battery 11 increases from 25 mm to L2=35 mm. At this time, the expansion deformation value of the single battery 11 is △L=10, and the deformation rate is =(L2- L1) / L1=10 / 25=4%; deformation rate When either of the two is within the respective preset range, it means that the battery pack 100 is in a state of thermal runaway. In order to ensure the accuracy of the judgment, it is necessary to obtain not only the deformation rate , it is also necessary to obtain the deformation rate F(t), because the single battery 11 will expand due to the influence of the environment or long-term use. If only the deformation rate is monitored When a single battery 11 experiences thermal runaway, it will expand in a relatively short period of time. If the monitored deformation rate F(t) meets the preset conditions, it will serve as the basis for subsequent judgments, allowing for a more accurate determination of whether the battery is in a thermal runaway state and avoiding misjudgments.

[0045] Step S22: Determine the deformation rate Whether it is within a first preset range, and whether the deformation rate F(t) is within a second preset range.

[0046] The deformation rate of the single battery 11 is obtained in the previous step. After determining the deformation rate F(t), a judgment is made within the preset range in this step.

[0047] Specifically, the first preset range is: And / or the second preset range is: 0.4% / s<F(t)<2% / s.

[0048] Step S23: If yes, it indicates that the battery pack is in a thermal runaway state.

[0049] In the above steps, if the deformation rate is obtained The value is 2%< <8%, and / or the deformation rate F(t) is within the range of 0.4% / s<F(t)<2% / s;

[0050] This indicates that the battery pack 100 is in a thermal runaway state.

[0051] Since square batteries have different thicknesses, the thicker the square battery, the greater the deformation, so the deformation range is set to 2% < <8%; at the same time, set the deformation rate to 0.4% / s<F(t)<2% / s. If either the range of and the range of F(t) are within the aforementioned preset ranges, it indicates that a single cell 11 in the battery pack 100 has experienced thermal runaway, and the battery pack 100 is in a thermal runaway state. When both values ​​are within the aforementioned preset ranges, it can be accurately determined that the battery pack 100 is in a thermal runaway state, reducing the possibility of misjudgment.

[0052] For example, in the two examples listed above, =2%, F(t)≈0.67%, which is consistent with 2%< <8% and 0.4% / s<F(t)<2% / s; and =4%, F(t)=1%, which is consistent with 2%< <8% and 0.4% / s<F(t)<2% / s, it means that the battery pack 100 is in a thermal runaway state.

[0053] In order to ensure the accuracy of the judgment, the deformation rate of the single battery 11 is obtained by the monitoring structure 30. Before the step of measuring the deformation rate F(t) within a preset time t, the thermal runaway monitoring method of the battery pack 100 further includes:

[0054] Obtaining the voltage and temperature of the battery pack 100;

[0055] Determine whether a ratio x of a voltage drop value to an initial voltage value during a preset time period t' is within a third preset range, and determine whether a temperature rise rate y during the preset time period t' is within a fourth preset range;

[0056] If so, the step of obtaining the expansion deformation value ΔL of the single battery (11) through the monitoring structure (30) is performed.

[0057] In order to avoid misjudgment, when obtaining the deformation rate Before obtaining the value of the expansion deformation value △L of the single cell 11, it is also necessary to obtain the voltage and temperature inside the battery pack 100, and determine whether the voltage drop value and temperature rise rate within the preset time period t' are within their respective preset ranges. When the voltage drop value and temperature rise rate within the preset time period t' also meet the conditions, the subsequent step of obtaining the expansion deformation value △L of the single cell 11 is performed, thereby ensuring the accuracy of determining whether the battery pack 100 is in a thermal runaway state.

[0058] The initial voltage of the battery pack is V1, the voltage at the preset time period t' is V2, the voltage drop △V = (V2-V1), and the ratio of the voltage drop to the initial voltage is x = △V / V1*100%. The initial temperature of the battery pack is T1, the temperature at the preset time period t' is T2, and the temperature rise rate y = (T2-T1) / t*100%.

[0059] Specifically, in some embodiments, the preset time period t'≥3s; the third preset range is the voltage drop value range x≥25%; and the fourth preset range is the temperature rise rate y≥1°C / s.

[0060] For example, the initial voltage value of the battery pack 100 is V1=100v. When the voltage value drops to V2=70v, the voltage drop value △V=V2-V1=100-70=30v, and the voltage drop value x=30 / 100*100%=30%. 30%>25%, which meets the third preset range. At the same time, the initial temperature of the battery pack 100 is T1=60. During the time period t'=3s, the temperature of the battery pack 100 reaches T2=70℃. At this time, the temperature rise rate = In accordance with the fourth preset range, the voltage drop value and temperature rise rate of the battery pack 100 are both in accordance with their respective preset ranges, combined with the deformation rate in some embodiments. By judging together with the deformation rate F(t), it can be determined that the battery pack 100 is in a thermal runaway state, thus avoiding misjudgment.

[0061] It should be noted that when the thermal runaway monitoring method of the battery pack 100 in some embodiments is used to monitor the battery pack 100 for thermal runaway, when the single cell 11 is in a high SOC (State of Charge) or low SOH (State of Health) state, the single cell 11 is in a swollen state due to cyclic gas production. At this time, the risk of thermal runaway of the single cell 11 is higher. Therefore, the strain gauge 31 monitors the thermal runaway of the single cell 11 at EOL (End of Line) more accurately and can avoid false alarms.

[0062] In another embodiment, the present application further provides a vehicle, which includes a main body and the above-mentioned battery pack 100, wherein the battery pack 100 is installed on the main body.

[0063] In the above vehicle, since the battery pack installed on the main body is provided with a monitoring structure 30, the monitoring structure 30 can obtain the deformation value △L of the single battery 11 in the battery pack, and the expansion deformation value △L is transmitted to the BMS40, and the BMS40 obtains the deformation rate through the expansion deformation value △L. And the deformation rate F(t) within the preset time, BMS40 calculates the deformation rate according to the deformation rate and deformation rate F(t) to determine whether the battery pack 100 is in a state of thermal runaway. If so, the BMS 40 can perform the next alarm action. In this way, by monitoring the expansion deformation value △L of the single battery 11 in the battery pack 100 after expansion when thermal runaway occurs, the basis for judging whether the battery pack 100 is in a state of thermal runaway can be obtained. Compared with the method of monitoring the temperature change or pressure change of the battery pack 100, it is less affected by the surrounding environment and has higher accuracy, thereby improving the safety of the vehicle during use.

Claims

1. A battery pack (100), comprising: A battery pack (10) comprising a plurality of single cells (11) stacked in sequence; An end plate (20) is arranged at an end of the battery pack (10) along the stacking direction of the single batteries (11); A monitoring structure (30) is provided on a side surface parallel to at least one of the single cells (11) and the end plate (20), and is configured to monitor the expansion deformation value of the single cell (11); The BMS (40) is electrically connected to the monitoring structure (30) and is configured to calculate the deformation rate and the deformation speed within a preset time according to the expansion deformation value, so as to determine whether the battery pack (100) is in a thermal runaway state according to the deformation rate and the deformation speed.

2. The battery pack (100) according to claim 1, wherein: The monitoring structure (30) comprises a strain gauge (31).

3. The battery pack (100) according to claim 2, wherein: The monitoring structure (30) further comprises an insulating protective member (32), wherein the insulating protective member (32) is coated on the outside of the strain gauge (31).

4. The battery pack (100) according to any one of claims 1 to 3, wherein: Along the stacking direction of the single cells (11), the monitoring structure (30) is arranged on the single cells (11) at the end of the battery pack (10), and is arranged on a side of the single cells (11) facing the end plate (20).

5. The battery pack (100) according to claim 4, wherein: Along the stacking direction of the single cells (11), the single cells (11) at both ends of the battery pack (10) are provided with the monitoring structure (30).

6. The battery pack (100) according to any one of claims 1 to 3 or 5, wherein: Along the stacking direction of the single battery (11), the thickness of the monitoring structure (30) ranges from 0.2 mm to 0.3 mm.

7. A vehicle, comprising a main body and a battery pack (100) according to any one of claims 1 to 6, wherein the battery pack (100) is mounted on the main body.

8. Thermal runaway monitoring methods, including: The expansion deformation value ΔL of the single battery (11) in the battery pack (100) is obtained through the monitoring structure (30), and the BMS (40) calculates the deformation rate of the single battery (11) according to the expansion deformation value ΔL and the deformation rate F(t) within a preset time t; Determine the deformation rate whether the deformation rate F(t) is within a first preset range, and whether the deformation rate F(t) is within a second preset range; If so, it is determined that the battery pack (100) is in a state of thermal runaway.

9. The thermal runaway monitoring method according to claim 8, wherein: The initial thickness of the single battery (11) is L1, the thickness after expansion during thermal runaway is L2, the expansion deformation value ΔL= L2-L1, and the deformation rate of the single battery (11) is = (L2- L10) / L1*100%, deformation rate within the preset time t .

10. The thermal runaway monitoring method according to claim 8, wherein: The first preset range is: 2%< <8%; and / or The second preset range is: 0, 4% / s<F(t)<2% / s.

11. The thermal runaway monitoring method according to any one of claims 8 to 10, wherein: The expansion deformation value ΔL of the single battery (11) is obtained through the monitoring structure (30), and the deformation rate of the single battery (11) is calculated according to the expansion deformation value ΔL. Before the step of measuring the deformation rate F(t) within a preset time t, the thermal runaway monitoring method of the battery pack (100) further comprises: Acquiring the voltage and temperature of the battery pack (100); Determine whether the ratio x of the voltage drop value to the initial voltage value during the preset time period t' is within a third preset range, and determine whether the temperature rise rate y during the preset time period t' is within a fourth preset range; If so, the step of obtaining the expansion deformation value ΔL of the single battery (11) through the monitoring structure (30) is performed.

12. The thermal runaway monitoring method according to claim 11, wherein: The preset time period t'≥3s; The third preset range is x ≥ 25%; The fourth preset range is y≥1°C / s.

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